Crown polyethers or macrocyclic polyethers are neutral compounds containing 4-20 oxygen atoms each separated from the next by two or more carbon atoms. They have been found to form stable complexes with salts of certain metals and with ammonium salts; "Macrocyclic Polyethers and Their Complexes", C. J. Pederson et al., ANGEW, CHEM. Internat, Edit., Vol. 11, page 16, (1972); and U.S. Pat. Nos. 3,562,295 and 3,687,978. Crown polyethers are believed to form salt-polyether complexes in which the cation is encircled by the oxygen atoms of the polyether ring and is held there by the electrostatic attraction between the cation and the negative ends of the carbon-oxygen dipoles. Since the stereo models of crown polyethers give a crown-like appearance, they are commonly designated as N-crown-M polyethers, wherein N is the total number of atoms in the polyether ring and M is the number of oxygen atoms in the polyether ring.
The crown polyethers ranging in size from cyclic tetramers of ethylene oxide (12-crown-4) and of oxetane (16-crown-4) to 60-membered polyether rings (dibenzo 60-crown-20) have been reported. The most effective complexing agents are said to be found among those polyethers containing 5-10 oxygen atoms each separated from the next by two carbon atoms.
Because of their ability to form complexes with alkali and alkaline earth cations they have been used extensively as phase-transfer catalysts in many organic reactions. However, the application of crown polyethers in industrial processes has been hampered by their toxicity. A further disadvantage is caused by high initial cost and the subsequent inability to recover and recycle the crown polyether because of its solubility in water and other solvents. A need has therefore existed for a crown substituted polyether capable of attaching to a resin or other insoluble inert supportive material. Crown polyether compounds attached to inert supportive materials in this manner are thus prevented from becoming exposed to workers and the environment; and are easily recoverable for reuse.
While crown polyethers are themselves well-known, substituted crown polyethers capable of covalently bonding to inert supportive materials have not been generally produced. Cinouini et al. in Journal of Chem. Soc., Chem. Commun., 394 (1976) described a synthesis of the following alkylamine-substituted crown polyether: ##STR1##
While this substituted crown polyether is capable of bonding to an inert supportive material there are certain disadvantages in its use. First, the molecule will likely attach to a supportive material through formation of an amide or imide. In these cases the bonding will be sensitive to strong alkali, as found under some phase-transfer conditions. Furthermore when attached to a commonly used supportive material such as chloromethylated polystyrene, the bonding will generate secondary amine functionality. The presence of this secondary amine functionality will interfere with the activity of the crown polyether moiety by reacting with acids and itself complexing with metal ions. The amine groups may also interfere if the resin is used in nucleophilic displacement reactions by reacting with the substrate.
It would be desirable to produce a substituted crown polyether capable of attaching to inert supportive materials that does not have the concommitant disadvantages of the prior art.
Other known crown polyether derivatives include benzene derivatives such as: ##STR2## disclosed in Varma, A. J., et al., J. Poly. Sci., Poly. Chem. Ed., 15, 1189 (1977) and: ##STR3## disclosed by VonVogtle, F., et al., Tetrahedron Letters, 4895 (1976).
U.S. Pat. No. 4,139,539 to Thomas A. Chamberlin et al., and 4,140,847 to Jon A. Orvik et al., disclose compounds having formulas ##STR4## respectively. In both instances the macrocyclic polyether compounds are disubstituted such that both substituents are attached to the same methylene moiety. Furthermore the disubstituted methylene moiety is attached on both sides in the ether ring to other methylene moieties.